Tolerance is an important component of alcohol abuse and alcoholism. We have been using magnocellular neurons from the hypothalamic-neurohypophysial system (HNS) to further our understanding of the acute and chronic actions of alcohol. One of the major advantages of this system is the physical separation of cell bodies in the supraoptic nucleus of the hypothalamus and accessible nerve terminals in the neurohypophysis. This unique property has allowed us to determine that ion channels in the two subcellular compartments differ significantly in their response to alcohol. The work proposed will build on findings that two components of potassium channel tolerance (decreased sensitivity and altered channel density) are present in the terminal, are intrinsic, and demonstrate different kinetics. We will capitalize on the special features of our recently developed HNS explant culture, which allows the independent examination of terminal and cell body compartments, and lends itself to finely-tuned drug exposure protocols and electrophysiological readout of channel function. We now propose to: 1) complete a characterization of tolerance in a functionally coupled Ca channel-potassium channel dyad, allowing a description of this important process in the nerve terminal, compared with the more typically studied cell body, 2) examine the independent capabilities and interdependencies of the somatic and terminal compartments for tolerance development, and 3) test the hypothesis that there are temporally-triggered switches tripped by drug exposure, that are associated with development of channel tolerance in cell bodies and terminals of the HNS. Our findings will provide a cellular model that will illuminate studies of tolerance at the behavioral level, and potentially contribute to effective treatments for alcoholism.